1. Field of the Invention
The invention generally relates to systems and methods for securing graft material to intraluminal devices.
2. Related Art
Intraluminal devices are commonly used in the treatment of diseased or impaired blood vessels in order to improve the performance of the diseased or impaired blood vessel. Such vascular diseases or impairments may include stenosis, thrombosis, occlusion or an aneurysm. Stents are a typical intraluminal device used to treat such diseased or impaired blood vessels.
A stent is generally a tubular device formed of biocompatible material that is implanted into a vessel to open and support the vessel. A stent is typically open ended and radially expandable to a diameter larger than its insertion diameter. In some cases, a stent may include a graft, i.e., a material attached to the stent, in order to provide an artificial lumen through which blood flow proceeds. Such a graft is typically comprised of bio-compatible material, such as polytetrafluoroethylene (PTFE) or expanded PTFE (ePTFE), having a microporous structure that enable tissue ingrowth and endothelialization once implanted at the intended location in the vascular system. Often, the means of attaching the graft material to a stent reduces the flexibility of the intraluminal device and increases the width of the device.
In the case of an aneurysm, an abnormal dilation of a layer or layers of an arterial wall occurs, usually as a result of a systemic collagen synthetic or structural defect. An abdominal aortic aneurysm is an aneurysm in the abdominal portion of the aorta, usually located in or near one or both of the two iliac arteries or near the renal arteries. The aneurysm often arises in the infrarenal portion of the diseased aorta, for example, below the kidneys. A thoracic aortic aneurysm, on the other hand, is an aneurysm in the thoracic portion of the aorta. When left untreated, the aneurysm may rupture, usually causing rapid fatal hemorrhaging.
A ruptured abdominal aortic aneurysm is presently the thirteenth leading cause of death in the United States. The routine management of abdominal aortic aneurysms has been surgical bypass, with the placement of a graft in the involved or dilated segment. Although resection with a synthetic graft, via transperitoneal or retroperitoneal procedures, has been the standard treatment, it is associated with significant risk. For example, complications include myocardial ischemia, renal failure, erectile impotence, intestinal ischemia, infection, lower limb ischemia, spinal cord injury with paralysis, aorta-enteric fistula, and death. Surgical treatment of abdominal aortic aneurysms is associated with an overall mortality rate of five percent in asymptomatic patients, sixteen to nineteen percent in symptomatic patients, and as high as fifty percent in patients with ruptured abdominal aortic aneurysms.
Disadvantages associated with conventional surgery, in addition to the high mortality rate, include an extended recovery period associated with the large incision and opening of the abdominal cavity, difficulties suturing the graft to the aorta, the loss of existing thrombosis to support and reinforce the graft, the unsuitability of certain patients for abdominal surgery, and the problems associated with such surgery after rupture of an aneurysm. The recovery and convalescent period often includes up to two weeks in the hospital and up to several months more at home, particularly if complications occur. Further, because many patients having abdominal aortic aneurysms are older, with other chronic illnesses, such patients are less than ideal candidates for such surgery.
Although abdominal aortic aneurysms are the most commonly occurring aneurysms, the occurrence of aneurysms is not limited to such abdominal regions. For example, thoracic aortic aneurysms also occur. Such thoracic aortic aneurysms require similar surgery, which is a major undertaking with associated high risks and significant mortality and morbidity.
Recently, less invasive, catheter-directed endovascular techniques have been developed for treating aneurysms, and abdominal aortic aneurysms in particular. The development of vascular stents, used in conjunction with graft material, has facilitated these less invasive treatment techniques. Shorter hospital stays, reduced periods of convalescence, and lower morbidity and mortality rates have occurred as a result.
The delivery procedure for such stent grafts typically involves advanced angiographic techniques performed through vascular accesses gained via surgical cutdown of a remote artery, such as the brachial or femoral artery. An appropriate sized introducer is placed over a guidewire and into the remote artery. Through the introducer, the stent graft is advanced to an intended treatment site via a delivery catheter. Typical deployment of the stent graft requires withdrawal of an outer sheath of the delivery catheter while maintaining the position of the stent graft with an inner stabilizing device. Most stent grafts are comprised of self-expanding materials; however, an additional angioplasty procedure, such as balloon angioplasty, may be required to secure the stent graft in place as desired at the intended treatment site. Thereafter, the introducer, guidewire, and the various components of the delivery catheter are withdrawn.
Due to the large diameters of the above described devices, typically greater than 20 French (3 F=1 mm), arteriotomy closure often requires open surgical repairs. Moreover, the manner in which the graft material is attached to the stent can undesirably increase the profile of the stent graft, rendering emplacement of the stent graft more difficult, and risking unintended and undesirable injury to the vessel during delivery and deployment to the intended treatment site.
In view of the above, a need exists for systems and methods that more reliably secure graft material to a stent structure without hindering the flexibility and radial stiffness of the stent graft. Ideally, such systems and methods would more reliably secure graft material to a stent structure in a manner enabling a reduction in the profile of the stent graft in a crimped state so as to improve the delivery and positioning of the stent graft at an intended treatment site.